use pointer cursor for native select when not disabled

Author: Vivian Hu

src/lib/input/input.scss

@@ -142,6 +142,7 @@ select.mat-input-element {
   display: inline-flex;
   box-sizing: border-box;
   background-position: right center;
+  cursor: pointer;
 
   // Native multi-selects are rendered inline which
   // means that they shouldn't have a dropdown arrow.
@@ -152,5 +153,8 @@ select.mat-input-element {
   [dir='rtl'] & {
     background-position: left center;
   }
-}
 
+  &:not(:disabled) {
+    cursor: pointer;
+  }.
+}